(1) Field of the Invention
The present invention relates to an internal combustion engine equipped with an electronic controlled throttle system for operating a throttle valve equipped in an intake system of the engine to be opened and dosed by an actuator to a target position, and more specifically, to a fail-safe control technique in an engine comprising two accelerator position sensors and two throttle position sensors or comprising at least two throttle position sensors, wherein said fail-safe control is performed in case one sensor out of said two sensors fails to operate.
(2) Related Art of the Invention
Conventionally, an electronic controlled throttle system is known where the opening (position) of the throttle valve is electronically controlled based on the accelerator position (step-in quantity of the accelerator pedal) and the engine rotation speed and the like, so as to gain a target air quantity (Japanese Unexamined Patent Publication No. 7-180570).
Of such known electronic controlled throttle systems, the ones that are not equipped with a limp-home structure for mechanically linking the throttle valve by means of the accelerator operation through a wire and the like (full electronic controlled throttle system) are applied, for example, with the following system in case the drive system fails to operate. The system includes two accelerator position sensors and two throttle position sensors, and as for the accelerator position or opening, the smaller value of the two detection values is selected (so as to prevent excessive output), and as for the throttle valve position or opening, the value detected by the main throttle position sensor is used, wherein in some cases, the greater value of the two detection values is selected (the greater value is selected and the value is corrected to a smaller value by a feedback control, thereby preventing excessive output).
According to the fail-safe method in such full electronic controlled throttle system, when one of the two sensors fails to operate (hereinafter called single failure) and the control is switched to utilize only the value detected by the remaining working single sensor, the promptness of failure detection provided by equipping double sensors is lost. Therefore, when the remaining working sensor also breaks down, the change in engine output will become large for a period of time until the failure is judged to have occurred. For safety, such trouble must be prevented.
The present invention is aimed at solving such problem of the conventional system mentioned above. The object of the present invention is to enable the vehicle to travel at the minimum speed necessary (limp-home) while preventing the excessive increase of the engine output, when single failure occurs to either of the two accelerator position sensors or the two throttle position sensors.
Further object of the present invention is to prevent the excessive increase of the engine output by limiting either the absolute value and/or the increase rate of the output.
Another object of the present invention is to enable the vehicle to travel at a speed corresponding to need while preventing the excessive increase of the engine output, when single failure occurs to one of the two throttle position sensors.
Another object of the present invention is to prevent the excessive increase of the engine output more securely during single failure of the throttle position sensor.
Further object of the present invention is to prevent the stalling of the vehicle caused by unnecessary decrease of the engine output during single failure of the throttle position sensor.
In order to realize the above objects, a first fail-safe control method of an internal combustion engine with an electronic controlled throttle system according to the present invention comprises the steps of:
setting a target position of a throttle valve equipped in an intake system of the engine according to engine operating conditions including an accelerator position detected by one accelerator position sensor selected from two accelerator position sensors equipped to the engine;
operating the throttle valve to open and close by an actuator, so that the position of the throttle valve detected by one throttle position sensor selected from two throttle position sensors equipped to the engine reaches the target position; and
providing a limit to the increase in accelerator opening for the output characteristics of the selected accelerator position sensor, when one sensor out of the two accelerator position sensors or the two throttle position sensors fails to operate.
Further, a first fail-safe control apparatus of an internal combustion engine with an electronic controlled throttle system according to the present invention comprises:
two accelerator position sensors for detecting an accelerator position;
a target position setting device for setting a target position of a throttle valve equipped in an intake system of the engine according to engine operating conditions including the accelerator position detected by a selected one accelerator position sensor out of the two accelerator position sensors;
two throttle position sensors for detecting a position of the throttle valve;
a throttle valve driving device for opening and closing said throttle valve by an actuator, so that the position of the throttle valve detected by one throttle position sensor selected from the two throttle position sensors reaches the target position; and
an output characteristics limiting device for providing a limit to the increase in accelerator opening for the output characteristics of the selected accelerator position sensor, when one sensor out of the two accelerator position sensors or the two throttle position sensors fails to operate.
According to the first fail-safe control method or apparatus of an internal combustion engine with an electronic controlled throttle system of the present invention, when one sensor out of the two accelerator position sensors or the two throttle position sensors fails to operate, the detection value of the remaining sensor is utilized. When doing so, a limit to the increase in accelerator opening is provided for the output characteristics of the selected accelerator position sensor, so the increase in the throttle opening controlled based on the limited output characteristics will also be limited, thereby enabling the vehicle to travel at the minimum speed necessary (limp-home) while preventing the excessive increase in the engine output.
Further, the limit to the increase in accelerator opening may include a function to limit the absolute value of the accelerator position by an upper limit value.
This enables the absolute value of the accelerator position to be limited by an upper limit value, which limits the upper limit of the throttle position, and a limp-home control may be performed where the increase in the absolute speed is restrained.
Even further, the limit to the increase in accelerator opening may include a function to limit the increase change rate of the accelerator position by an upper limit change rate.
This enables the increase change rate of the accelerator position to be limited by an upper limit change rate, whereby the increase change rate of the throttle position is limited, and a limp-home control may be performed where rapid acceleration is restrained.
Even further, the limit to the increase in accelerator opening may include a function to limit the absolute value of the accelerator position by an upper limit value and a function to limit the increase change rate of the accelerator position by an upper limit change rate, and the smaller value between the accelerator position being limited by the upper limit value and the accelerator position being limited by the upper limit change rate may be selected.
Accordingly, by selecting through the output characteristics limiting device the smaller value out of the accelerator position limited of its absolute value by an upper limit value, and the accelerator position limited of its increase change rate by an upper limit change rate, the throttle valve position may be controlled according to the limited accelerator position characteristics, and a limp-home control may be performed where both rapid acceleration and increase in absolute speed are restrained.
Even further, the failure of one sensor out of the two accelerator position sensors or the two throttle position sensors may be determined when said one sensor fails to operate continuously for a predetermined time.
Accordingly, a transitional failure of the sensor may be excluded, and only continuous failure of the sensor may be determined as single failure.
Next, according to a second fail-safe control method of an internal combustion engine with an electronic controlled throttle system, said method comprises the steps of:
setting a target position of a throttle valve equipped in an intake system of the engine according to engine operating conditions including an accelerator position detected by an accelerator position sensor;
operating the throttle valve to open and close by an actuator, so that the position of the throttle valve detected by one throttle position sensor selected from the two throttle position sensors equipped to the engine reaches the target position; and
setting a fuel injection quantity based on a detection value of the accelerator position and a detection value of engine rotation speed detected by an engine rotation speed detecting device, when one sensor out of the two throttle position sensors fails to operate.
Further, a second fail-safe control apparatus of an internal combustion engine with an electronic controlled throttle system according to the present invention comprises:
an accelerator position sensor for detecting an accelerator position;
a target position setting device for setting a target position of a throttle valve equipped in an intake system of the engine according to engine operating conditions including the accelerator position detected by the accelerator position sensor,
two throttle position sensors for detecting a position of said throttle valve;
a throttle valve driving device for opening and closing the throttle valve by an actuator, so that the position of the throttle valve detected by one throttle position sensor selected from the two throttle position sensors reaches the target position; and
a fuel injection quantity setting device during failure for setting a fuel injection quantity based on a detection value of the accelerator position and a detection value of engine rotation speed by an engine rotation speed detecting device, when one sensor out of the two throttle position sensors fail to operate.
According to the second fail-safe control method or apparatus of an internal combustion engine with an electronic controlled throttle system of the present invention, when one of the two throttle position sensors fails to operate, the detection value of the remaining working sensor is used to feed-back control the position of the throttle valve. In this case, even if a situation occurs where the position of the throttle valve may be increased abnormally, since the fuel injection quantity is set based on the engine rotation speed and the accelerator position detected by the accelerator position sensor operated by the will of the driver, even when the intake air quantity is increased by the increase in throttle valve opening, the increase in fuel injection quantity may be restrained without depending on the increase in intake air quantity. Moreover, the excessive limitation on the engine output caused by limiting the throttle valve position to a default position and the like will not occur. Therefore, the desired engine output may be gained by setting an appropriate fuel injection quantity.
Further, when both two throttle position sensors are working normally, the fuel injection quantity may be set based on the detection value of an intake air quantity by an intake air quantity detecting device and the detection value of the engine rotation speed.
Accordingly, when both two throttle position sensors are working normally, the fuel injection quantity may be controlled to a value corresponding highly accurately to the intake air quantity, based on the detection value of the intake air quantity and the detection value of the engine rotation speed.
In a third fail-safe control method of an internal combustion engine with an electronic controlled throttle system according to the invention, said method comprises the steps of:
setting a target position of a throttle valve equipped in an intake system of the engine according to engine operating conditions including an accelerator position detected by an accelerator position sensor;
operating the throttle valve to open and close by an actuator, so that the position of the throttle valve detected by one throttle position sensor selected from two throttle position sensors equipped to the engine reaches the target position;
when one sensor out of the two throttle position sensors fails to operate, setting a first fuel injection quantity based on a detection value of the accelerator position and a detection value of an engine rotation speed, and setting a second fuel injection quantity based on a detection value of a mass intake air quantity and a detection value of the engine rotation speed, and thereafter, selecting the smaller value of the two and setting the selected value; and
when both two throttle position sensors are working normally, setting the fuel injection quantity based on the detection value of the mass intake air quantity and the detection value of the engine rotation speed.
Further, a third fail-safe control apparatus of an internal combustion engine with an electronic controlled throttle system according to the present invention comprises:
an accelerator position sensor for detecting an accelerator position;
a target position setting device for setting a target position of a throttle valve equipped in an intake system of the engine according to engine operating conditions including the accelerator position detected by the accelerator position sensor;
two throttle position sensors for detecting a position of the throttle valve;
a throttle valve driving means for opening and closing said throttle valve by an actuator, so that the position of the throttle valve detected by one throttle position sensor selected from the two throttle position sensors reaches the target position; and
a fuel injection quantity switching/setting device for selecting and setting the smaller value out of a fuel injection quantity set based on a detection value of the accelerator opening and a detection value of engine rotation speed by an engine rotation speed detecting device, and a fuel injection quantity set based on a detection value of a mass intake air quantity by an intake air quantity detecting device and the detection value of the engine rotation speed when one sensor out of the two throttle position sensors fails to operate, and setting the fuel injection quantity based on the detection value of the mass intake air quantity and the detection value of the engine rotation speed when both two throttle position sensors are working normally.
In the second method or apparatus of the present invention, when the air density is reduced when traveling on highland and the like during the single failure of the throttle sensor, the accelerator position will be increased, therefore, when the fuel injection quantity is set based on the accelerator position and the engine rotation speed, the fuel injection quantity may become excessive. However, according to the third method or apparatus of the present invention mentioned above, when the fuel injection quantity is set based on the detection value of the mass intake air quantity and the detection value of the engine rotation speed, the value will not be effected by the decrease in air density, and as a result, the fuel injection quantity will not be set to an excessive value. Since the smaller value of the fuel injection quantity set as above is selected, the appropriate engine output may be guaranteed.
The second and third method and apparatus may include a function to set a lower limit value of the fuel injection quantity corresponding to a lower limit value of the throttle valve position set corresponding to a failure of the throttle position sensor, when one sensor out of the two throttle position sensors fails to operate.
Accordingly, when single failure occurs during the state where the accelerator position is set too small (for example, during a released state), even though the throttle valve is set to the lower limit value (default position) corresponding to such failure of the sensor, since the accelerator position is smaller than that value, there is a possibility that the vehicle may be stalled because of the delay in the rise of the fuel injection quantity caused by the excessively low fuel injection quantity being set based on the accelerator position and the engine rotation speed,. However, by setting the lower limit value of the fuel injection quantity in correspondence to the lower limit value of the throttle valve, such stalling may be prevented, and a stable limp-home function may be secured.
Further, the second and third method and apparatus may include two accelerator position sensors, and the detection value of either one of said sensors is selected and utilized.
By comprising two accelerator position sensors and selecting the detection value from either sensor, for example, the smaller value, the method and apparatus may deal with failure or abnormality more securely.